1. Field of the Invention
The present invention relates to a mobile terminal compatible with the IETF Mobile IP protocol that supports the mobility of mobile terminals in the Internet.
2. Description of the Related Art
For the mobile terminals to be connected to the Internet, the products according to the RFC 2002/3220 issued by the IETF (Internet Engineering Task Force) are increasing. FIG. 4 shows an exemplary configuration according to the IETF Mobile IP protocol as defined by RFC 2002/3220 that supports the mobility between subnets. A mobile terminal (Mobile Node: MN) 22 acquires an IP address (care-of address) to be used temporarily at a visited site subnet by using a DHCP (Dynamic Host Configuration Protocol) or the like. Then, the mobile terminal 22 transmits a mobility registration request (registration request: RRQ) 25 for registering information regarding the moving to a home agent (HA) 24. At this point, the transmission may be made either via a foreign agent (FA) 23 or directly to the home agent 24 at the subnet.
Here, the DHCP is a mechanism for allocating an IP address to a communication node on the Internet. Normally, a DHCP server exists on the network and allocates an IP address in response to a request from the communication node. According to this mechanism, there is no need to assign a fixed IP address to the communication node side in advance. The communication node is a terminal or network device connected to the network such as a mobile terminal, for example. Regardless of whether the mobility registration is successful or not, the home agent 24 transmits a mobility registration replay packet (registration reply: RRP) 26 to the mobile terminal 22 that has sent the mobility registration request (RRQ) 25. This mobility registration is an important step for making a location of the mobile terminal (MN) 22 apparent.
FIG. 6 shows an exemplary internal configuration of a conventional mobile terminal, which comprises a TCP/IP driver 1 for controlling the TCP/IP stack, a general application program 2 operated on the mobile terminal, a Mobile IP management program 3 for carrying out processing related to the Mobile IP, a network driver 4 for controlling a network card, and a network card 5 for carrying out physical Ethernet accesses.
Conventionally, the Mobile IP management program 3 implemented on the mobile terminal is carrying out communications related to the mobile IP by utilizing functions of the TCP/IP driver that is normally provided in the generally utilized OS (Operating System). This is often realized through a socket according to the WinSock specification, for example. The WinSock is a communication interface specification defined among vendors who provides softwares for processing the TCP/IP stack. The communications for setting up a connection with a communication node through such a socket can be realized relatively easily. However, such a processing within the OS presupposes the use for the general purpose, so that it is not necessarily usable exactly as intended.
The Mobile IP related packets include a mobility registration request (RRQ) packet and a mobility registration reply (RRP) packet. The Mobile IP management program 3 exchanges data with the TCP/IP driver 1 by using the socket of the TCP/IP driver provided in the OS. Then, a connection for communications with the home agent existing on the network has been established via the network driver 4 and the network card 5.
As such, the Mobile IP related packet communications that require urgency have conventionally been processed without making any distinction from those for packets of the other general application program. The socket of the TCP/IP driver that is normally provided in the OS usually processes the requested communications sequentially as they are requested. Consequently, even when requests to the OS are made by a plurality of programs simultaneously, there has conventionally been some possibility by which the packets that require urgency will not be processed at appropriate timings, as described above.
In order to avoid the above described problem, it is possible to prioritize specific packets. However, in this case, there is a need to carry out the priority control according to types of the received packets and the processing itself often becomes complicated. This can also be a cause for degrading the communication speed of the mobile terminal. In addition, even if the above described improvement is made at the application side, hardly any effect can be expected for the reason described above as long as the socket provided by the OS is used.
Also, in order for the mobile terminal to carry out communications while moving through connection target subnets, there is a need to acquire a temporal IP address (care-of address) by using the DHCP or the like at the visited site subnet. This temporal IP address is an IP address that must be acquired by the mobile terminal in order to carry out communications at a newly connected subnet. The similar considerations as in the case of the Mobile IP are also necessary for the exchange of packets regarding the DHCP or the like to acquire this temporal IP address.
Thus, the conventional communication function of the mobile terminal has been associated with the problems that the packets that require urgency such as those of the Mobile IP are not processed at appropriate timings or that the communication efficiency is insufficient.
Also, in the Mobile IP of the IPv6, a network prefix advertisement (neighbor advertisement) from an upstream router instead of DHCP, a neighbor solicitation packet by which the terminal inquires the upstream router, and a binding update packet for notifying a new location information at a time of moving must be similarly handled as control related packets to be subjected to the priority control.